This application requests continuation of the large population-based registry of insulin-dependent diabetes mellitus (IDDM) among African-American and Hispanic children in Chicago. The Registry project includes on average 49 African-American cases and 20 Hispanic incident cases per year. This represents more than three times the number of African-origin cases than in any other registry worldwide, and the largest number of Hispanic cases in the continental US. The investigators will use the Registry to investigate two questions of immediate relevance, as follow. 1. Ethnic differences in the natural history of IDDM: Recent attention has focused on the possibility that some young people initially diagnosed with IDDM actually have a variant form of diabetes. To date, no population-based data are available on the spectrum of diabetic disease in U.S. youth. Considering the high risk of NIDDM among both African-American and Hispanics, there may well be unique genetic and/or pathophysiologic processes at work in insulin-treated minority children. The investigators hypothesize that clinically atypical disease will be described in a substantial proportion (5-15%) of insulin-treated minority patients, and that it can be distinguished from autoimmune diabetes on the basis of family history, onset characteristics, and genetic markers. 2. IDDM outcomes among minorities: The investigators recently demonstrated that the case-fatality rate for IDDM in Chicago is nine times greater among African-American than non-Hispanic white patients through age 24, and there is some evidence of disparities in morbidity as well. They hypothesize that, controlled for duration, the rates of early signs of developing complications in registered minority patients will significantly exceed those reported elsewhere among non-Hispanic white patients. They will investigate whether the mortality rate among African-American patients exceeds that among Hispanic patients in Chicago, and if mortality among both African-American and Hispanic patients exceed published rates elsewhere. They will accomplish the following specific tasks: 1) continue the incidence registry of IDDM among minority children in the City of Chicago; 2) determine the prevalence of atypical diabetes among these insulin-treated, youth onset patients; 3) construct a score to predict the subsequent clinical course of atypical diabetes in young minority patients; and 4) describe the natural history of diabetes complications and mortality in minority young people with IDDM.